Carrier Infinity 50XL Product Data page 22

CONTROLS
Sequence of Operation
The packaged air conditioner is designed for installation with a
communicating Infinity User Interface. This unit will not respond to
commands provided by a common thermostat except under certain
emergency situations.
The User Interface uses temperature, humidity and other data
supplied from indoor and outdoor system components to control
heating or cooling system for optimum comfort. The unit will be
commanded by the User Interface to supply airflow. The unit will
operate the indoor blower at requested airflow for most modes.
The nominal requested airflow, in high stage, will be 350 cfm per ton
of nominal cooling capacity as defined by unit size. Actual airflow
request will be adjusted from nominal using indoor and outdoor
temperature and indoor humidity data to optimize the system
operation for occupant comfort and system efficiency. Refer to User
Interface literature for further system control details.
Airflow during electric heater operation must be greater than a
minimum level for safe operation. If User Interface instructs unit to
turn on electric heat and the requested airflow is less than the
minimum level the unit control will override requested value.
With a call for first stage cooling, the outdoor fan and low- -stage
compressor are energized. If low- -stage cannot satisfy cooling
demand, high- -stage is energized by the User Interface. After
second stage is satisfied, the unit returns to low- -stage operation
until first stage is satisfied or until second stage is required again.
When both first stage and second stage cooling are satisfied, the
compressor will shut off.
NOTE: When two- -stage unit is operating at low stage, system vapor
(suction) pressure will be higher than a standard single- -stage system
or high- -stage operation.
NOTE: Outdoor fan motor will continue to operate for one
minute after compressor shuts off, when outdoor ambient is greater
than or equal to 100°F (37.7°C).
UTILITY INTERFACE WITH INFINITY CONTROL
The utility curtailment relay should be connected to factory
supplied pigtails (PINK connected to R, VIOLET connected to Y2
on the control board) located in the low voltage splice box (see
Typical Wiring Schematic ). This input allows a power utility
device to interrupt compressor operation during peak load periods.
When the utility sends a signal to shut the system down, the UI will
display "Curtailment Active".
Infinity Controlled Low Ambient Cooling
NOTE: When this unit is operating below 55_F (12.7°C) outdoor
temperature, provisions must be made for low ambient operation.
This unit is capable of low ambient cooling down to 0_F (- -17.7°C)
ONLY when using the Infinity control. A low ambient kit is not
required, and the outdoor fan motor does not need to be replaced for
Infinity controlled low ambient operation. Low ambient cooling
must be enabled in the UI set- -up. Fan may not begin to cycle until
about 40_F (4.4°C) OAT. Fan will cycle based on coil and outdoor
air temperature.
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